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//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "assembler"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCSectionMachO.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/MachO.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/Debug.h"
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#include "../Target/X86/X86FixupKinds.h"
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class MachObjectWriter;
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STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
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// FIXME FIXME FIXME: There are number of places in this file where we convert
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// what is a 64-bit assembler value used for computation into a value in the
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// object file, which may truncate it. We should detect that truncation where
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// invalid and report errors back.
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static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
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MachObjectWriter &MOW);
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static uint64_t WriteNopData(uint64_t Count, MachObjectWriter &MOW);
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/// isVirtualSection - Check if this is a section which does not actually exist
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/// in the object file.
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static bool isVirtualSection(const MCSection &Section) {
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const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
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unsigned Type = SMO.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
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return (Type == MCSectionMachO::S_ZEROFILL);
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static unsigned getFixupKindLog2Size(unsigned Kind) {
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default: llvm_unreachable("invalid fixup kind!");
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case X86::reloc_pcrel_1byte:
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case FK_Data_1: return 0;
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case FK_Data_2: return 1;
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case X86::reloc_pcrel_4byte:
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case X86::reloc_riprel_4byte:
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case FK_Data_4: return 2;
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case FK_Data_8: return 3;
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static bool isFixupKindPCRel(unsigned Kind) {
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case X86::reloc_pcrel_1byte:
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case X86::reloc_pcrel_4byte:
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case X86::reloc_riprel_4byte:
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class MachObjectWriter {
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// See <mach-o/loader.h>.
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Header_Magic32 = 0xFEEDFACE,
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Header_Magic64 = 0xFEEDFACF
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static const unsigned Header32Size = 28;
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static const unsigned Header64Size = 32;
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static const unsigned SegmentLoadCommand32Size = 56;
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static const unsigned Section32Size = 68;
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static const unsigned SymtabLoadCommandSize = 24;
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static const unsigned DysymtabLoadCommandSize = 80;
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static const unsigned Nlist32Size = 12;
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static const unsigned RelocationInfoSize = 8;
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HF_SubsectionsViaSymbols = 0x2000
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enum LoadCommandType {
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// See <mach-o/nlist.h>.
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enum SymbolTypeType {
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STT_Undefined = 0x00,
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enum SymbolTypeFlags {
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// If any of these bits are set, then the entry is a stab entry number (see
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// <mach-o/stab.h>. Otherwise the other masks apply.
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STF_StabsEntryMask = 0xe0,
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STF_PrivateExtern = 0x10
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/// IndirectSymbolFlags - Flags for encoding special values in the indirect
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enum IndirectSymbolFlags {
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ISF_Local = 0x80000000,
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ISF_Absolute = 0x40000000
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/// RelocationFlags - Special flags for addresses.
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enum RelocationFlags {
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RF_Scattered = 0x80000000
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enum RelocationInfoType {
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RIT_PreboundLazyPointer = 3,
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RIT_LocalDifference = 4
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/// MachSymbolData - Helper struct for containing some precomputed information
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struct MachSymbolData {
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MCSymbolData *SymbolData;
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uint64_t StringIndex;
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uint8_t SectionIndex;
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// Support lexicographic sorting.
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bool operator<(const MachSymbolData &RHS) const {
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const std::string &Name = SymbolData->getSymbol().getName();
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return Name < RHS.SymbolData->getSymbol().getName();
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MachObjectWriter(raw_ostream &_OS, bool _IsLSB = true)
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: OS(_OS), IsLSB(_IsLSB) {
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/// @name Helper Methods
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void Write8(uint8_t Value) {
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void Write16(uint16_t Value) {
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Write8(uint8_t(Value >> 0));
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Write8(uint8_t(Value >> 8));
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Write8(uint8_t(Value >> 8));
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Write8(uint8_t(Value >> 0));
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void Write32(uint32_t Value) {
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Write16(uint16_t(Value >> 0));
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Write16(uint16_t(Value >> 16));
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Write16(uint16_t(Value >> 16));
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Write16(uint16_t(Value >> 0));
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void Write64(uint64_t Value) {
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Write32(uint32_t(Value >> 0));
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Write32(uint32_t(Value >> 32));
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Write32(uint32_t(Value >> 32));
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Write32(uint32_t(Value >> 0));
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void WriteZeros(unsigned N) {
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const char Zeros[16] = { 0 };
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for (unsigned i = 0, e = N / 16; i != e; ++i)
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OS << StringRef(Zeros, 16);
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OS << StringRef(Zeros, N % 16);
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void WriteString(StringRef Str, unsigned ZeroFillSize = 0) {
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WriteZeros(ZeroFillSize - Str.size());
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void WriteHeader32(unsigned NumLoadCommands, unsigned LoadCommandsSize,
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bool SubsectionsViaSymbols) {
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if (SubsectionsViaSymbols)
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Flags |= HF_SubsectionsViaSymbols;
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// struct mach_header (28 bytes)
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uint64_t Start = OS.tell();
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Write32(Header_Magic32);
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// FIXME: Support cputype.
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Write32(MachO::CPUTypeI386);
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// FIXME: Support cpusubtype.
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Write32(MachO::CPUSubType_I386_ALL);
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Write32(NumLoadCommands); // Object files have a single load command, the
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Write32(LoadCommandsSize);
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assert(OS.tell() - Start == Header32Size);
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/// WriteSegmentLoadCommand32 - Write a 32-bit segment load command.
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/// \arg NumSections - The number of sections in this segment.
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/// \arg SectionDataSize - The total size of the sections.
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void WriteSegmentLoadCommand32(unsigned NumSections,
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uint64_t SectionDataStartOffset,
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uint64_t SectionDataSize) {
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// struct segment_command (56 bytes)
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uint64_t Start = OS.tell();
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Write32(LCT_Segment);
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Write32(SegmentLoadCommand32Size + NumSections * Section32Size);
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Write32(0); // vmaddr
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Write32(VMSize); // vmsize
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Write32(SectionDataStartOffset); // file offset
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Write32(SectionDataSize); // file size
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Write32(0x7); // maxprot
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Write32(0x7); // initprot
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Write32(NumSections);
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assert(OS.tell() - Start == SegmentLoadCommand32Size);
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void WriteSection32(const MCSectionData &SD, uint64_t FileOffset,
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uint64_t RelocationsStart, unsigned NumRelocations) {
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// The offset is unused for virtual sections.
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if (isVirtualSection(SD.getSection())) {
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assert(SD.getFileSize() == 0 && "Invalid file size!");
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// struct section (68 bytes)
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uint64_t Start = OS.tell();
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// FIXME: cast<> support!
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const MCSectionMachO &Section =
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static_cast<const MCSectionMachO&>(SD.getSection());
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WriteString(Section.getSectionName(), 16);
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WriteString(Section.getSegmentName(), 16);
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Write32(SD.getAddress()); // address
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Write32(SD.getSize()); // size
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unsigned Flags = Section.getTypeAndAttributes();
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if (SD.hasInstructions())
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Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS;
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assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
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Write32(Log2_32(SD.getAlignment()));
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Write32(NumRelocations ? RelocationsStart : 0);
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Write32(NumRelocations);
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Write32(0); // reserved1
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Write32(Section.getStubSize()); // reserved2
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assert(OS.tell() - Start == Section32Size);
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void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
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uint32_t StringTableOffset,
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uint32_t StringTableSize) {
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// struct symtab_command (24 bytes)
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uint64_t Start = OS.tell();
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Write32(SymtabLoadCommandSize);
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Write32(SymbolOffset);
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Write32(StringTableOffset);
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Write32(StringTableSize);
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assert(OS.tell() - Start == SymtabLoadCommandSize);
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void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
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uint32_t NumLocalSymbols,
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uint32_t FirstExternalSymbol,
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uint32_t NumExternalSymbols,
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uint32_t FirstUndefinedSymbol,
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uint32_t NumUndefinedSymbols,
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uint32_t IndirectSymbolOffset,
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uint32_t NumIndirectSymbols) {
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// struct dysymtab_command (80 bytes)
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uint64_t Start = OS.tell();
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Write32(LCT_Dysymtab);
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Write32(DysymtabLoadCommandSize);
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Write32(FirstLocalSymbol);
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Write32(NumLocalSymbols);
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Write32(FirstExternalSymbol);
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Write32(NumExternalSymbols);
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Write32(FirstUndefinedSymbol);
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Write32(NumUndefinedSymbols);
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Write32(0); // tocoff
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Write32(0); // modtaboff
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Write32(0); // nmodtab
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Write32(0); // extrefsymoff
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Write32(0); // nextrefsyms
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Write32(IndirectSymbolOffset);
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Write32(NumIndirectSymbols);
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Write32(0); // extreloff
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Write32(0); // nextrel
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Write32(0); // locreloff
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Write32(0); // nlocrel
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assert(OS.tell() - Start == DysymtabLoadCommandSize);
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void WriteNlist32(MachSymbolData &MSD) {
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MCSymbolData &Data = *MSD.SymbolData;
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const MCSymbol &Symbol = Data.getSymbol();
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uint16_t Flags = Data.getFlags();
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uint32_t Address = 0;
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// Set the N_TYPE bits. See <mach-o/nlist.h>.
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// FIXME: Are the prebound or indirect fields possible here?
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if (Symbol.isUndefined())
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Type = STT_Undefined;
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else if (Symbol.isAbsolute())
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// FIXME: Set STAB bits.
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if (Data.isPrivateExtern())
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Type |= STF_PrivateExtern;
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if (Data.isExternal() || Symbol.isUndefined())
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Type |= STF_External;
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// Compute the symbol address.
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if (Symbol.isDefined()) {
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if (Symbol.isAbsolute()) {
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llvm_unreachable("FIXME: Not yet implemented!");
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Address = Data.getFragment()->getAddress() + Data.getOffset();
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} else if (Data.isCommon()) {
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// Common symbols are encoded with the size in the address
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// field, and their alignment in the flags.
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Address = Data.getCommonSize();
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// Common alignment is packed into the 'desc' bits.
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if (unsigned Align = Data.getCommonAlignment()) {
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unsigned Log2Size = Log2_32(Align);
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assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
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llvm_report_error("invalid 'common' alignment '" +
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// FIXME: Keep this mask with the SymbolFlags enumeration.
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Flags = (Flags & 0xF0FF) | (Log2Size << 8);
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// struct nlist (12 bytes)
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Write32(MSD.StringIndex);
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Write8(MSD.SectionIndex);
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// The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
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struct MachRelocationEntry {
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void ComputeScatteredRelocationInfo(MCAssembler &Asm, MCFragment &Fragment,
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const MCValue &Target,
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DenseMap<const MCSymbol*,MCSymbolData*> &SymbolMap,
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std::vector<MachRelocationEntry> &Relocs) {
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uint32_t Address = Fragment.getOffset() + Fixup.Offset;
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unsigned IsPCRel = 0;
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unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
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unsigned Type = RIT_Vanilla;
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const MCSymbol *A = Target.getSymA();
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MCSymbolData *SD = SymbolMap.lookup(A);
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uint32_t Value = SD->getFragment()->getAddress() + SD->getOffset();
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if (const MCSymbol *B = Target.getSymB()) {
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Type = RIT_LocalDifference;
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MCSymbolData *SD = SymbolMap.lookup(B);
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Value2 = SD->getFragment()->getAddress() + SD->getOffset();
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// The value which goes in the fixup is current value of the expression.
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Fixup.FixedValue = Value - Value2 + Target.getConstant();
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if (isFixupKindPCRel(Fixup.Kind)) {
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Fixup.FixedValue -= Address;
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MachRelocationEntry MRE;
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MRE.Word0 = ((Address << 0) |
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Relocs.push_back(MRE);
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if (Type == RIT_LocalDifference) {
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MachRelocationEntry MRE;
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MRE.Word0 = ((0 << 0) |
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Relocs.push_back(MRE);
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void ComputeRelocationInfo(MCAssembler &Asm, MCDataFragment &Fragment,
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DenseMap<const MCSymbol*,MCSymbolData*> &SymbolMap,
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std::vector<MachRelocationEntry> &Relocs) {
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if (!Fixup.Value->EvaluateAsRelocatable(Target))
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llvm_report_error("expected relocatable expression");
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// If this is a difference or a local symbol plus an offset, then we need a
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// scattered relocation entry.
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if (Target.getSymB() ||
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(Target.getSymA() && !Target.getSymA()->isUndefined() &&
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Target.getConstant()))
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return ComputeScatteredRelocationInfo(Asm, Fragment, Fixup, Target,
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uint32_t Address = Fragment.getOffset() + Fixup.Offset;
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unsigned IsPCRel = 0;
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unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
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unsigned IsExtern = 0;
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if (Target.isAbsolute()) { // constant
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// SymbolNum of 0 indicates the absolute section.
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// FIXME: When is this generated?
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llvm_unreachable("FIXME: Not yet implemented!");
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const MCSymbol *Symbol = Target.getSymA();
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MCSymbolData *SD = SymbolMap.lookup(Symbol);
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if (Symbol->isUndefined()) {
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Index = SD->getIndex();
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// The index is the section ordinal.
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MCAssembler::iterator it = Asm.begin(), ie = Asm.end();
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for (; it != ie; ++it, ++Index)
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if (&*it == SD->getFragment()->getParent())
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assert(it != ie && "Unable to find section index!");
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Value = SD->getFragment()->getAddress() + SD->getOffset();
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// The value which goes in the fixup is current value of the expression.
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Fixup.FixedValue = Value + Target.getConstant();
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if (isFixupKindPCRel(Fixup.Kind)) {
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Fixup.FixedValue -= Address;
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// struct relocation_info (8 bytes)
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MachRelocationEntry MRE;
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MRE.Word1 = ((Index << 0) |
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Relocs.push_back(MRE);
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void BindIndirectSymbols(MCAssembler &Asm,
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DenseMap<const MCSymbol*,MCSymbolData*> &SymbolMap) {
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// This is the point where 'as' creates actual symbols for indirect symbols
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// (in the following two passes). It would be easier for us to do this
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// sooner when we see the attribute, but that makes getting the order in the
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// symbol table much more complicated than it is worth.
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// FIXME: Revisit this when the dust settles.
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// Bind non lazy symbol pointers first.
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for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
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ie = Asm.indirect_symbol_end(); it != ie; ++it) {
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// FIXME: cast<> support!
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const MCSectionMachO &Section =
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static_cast<const MCSectionMachO&>(it->SectionData->getSection());
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Section.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
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if (Type != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
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MCSymbolData *&Entry = SymbolMap[it->Symbol];
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Entry = new MCSymbolData(*it->Symbol, 0, 0, &Asm);
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// Then lazy symbol pointers and symbol stubs.
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for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
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ie = Asm.indirect_symbol_end(); it != ie; ++it) {
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// FIXME: cast<> support!
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const MCSectionMachO &Section =
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static_cast<const MCSectionMachO&>(it->SectionData->getSection());
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Section.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
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if (Type != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
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Type != MCSectionMachO::S_SYMBOL_STUBS)
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MCSymbolData *&Entry = SymbolMap[it->Symbol];
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Entry = new MCSymbolData(*it->Symbol, 0, 0, &Asm);
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// Set the symbol type to undefined lazy, but only on construction.
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// FIXME: Do not hardcode.
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Entry->setFlags(Entry->getFlags() | 0x0001);
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/// ComputeSymbolTable - Compute the symbol table data
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/// \param StringTable [out] - The string table data.
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/// \param StringIndexMap [out] - Map from symbol names to offsets in the
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void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
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std::vector<MachSymbolData> &LocalSymbolData,
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std::vector<MachSymbolData> &ExternalSymbolData,
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std::vector<MachSymbolData> &UndefinedSymbolData) {
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// Build section lookup table.
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DenseMap<const MCSection*, uint8_t> SectionIndexMap;
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for (MCAssembler::iterator it = Asm.begin(),
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ie = Asm.end(); it != ie; ++it, ++Index)
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SectionIndexMap[&it->getSection()] = Index;
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assert(Index <= 256 && "Too many sections!");
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// Index 0 is always the empty string.
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StringMap<uint64_t> StringIndexMap;
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StringTable += '\x00';
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// Build the symbol arrays and the string table, but only for non-local
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// The particular order that we collect the symbols and create the string
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// table, then sort the symbols is chosen to match 'as'. Even though it
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// doesn't matter for correctness, this is important for letting us diff .o
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for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
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ie = Asm.symbol_end(); it != ie; ++it) {
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const MCSymbol &Symbol = it->getSymbol();
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// Ignore assembler temporaries.
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if (it->getSymbol().isTemporary())
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if (!it->isExternal() && !Symbol.isUndefined())
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uint64_t &Entry = StringIndexMap[Symbol.getName()];
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Entry = StringTable.size();
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StringTable += Symbol.getName();
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StringTable += '\x00';
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MSD.StringIndex = Entry;
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if (Symbol.isUndefined()) {
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MSD.SectionIndex = 0;
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UndefinedSymbolData.push_back(MSD);
669
} else if (Symbol.isAbsolute()) {
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MSD.SectionIndex = 0;
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ExternalSymbolData.push_back(MSD);
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MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
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assert(MSD.SectionIndex && "Invalid section index!");
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ExternalSymbolData.push_back(MSD);
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// Now add the data for local symbols.
680
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
681
ie = Asm.symbol_end(); it != ie; ++it) {
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const MCSymbol &Symbol = it->getSymbol();
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// Ignore assembler temporaries.
685
if (it->getSymbol().isTemporary())
688
if (it->isExternal() || Symbol.isUndefined())
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uint64_t &Entry = StringIndexMap[Symbol.getName()];
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Entry = StringTable.size();
694
StringTable += Symbol.getName();
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StringTable += '\x00';
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MSD.StringIndex = Entry;
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if (Symbol.isAbsolute()) {
703
MSD.SectionIndex = 0;
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LocalSymbolData.push_back(MSD);
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MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
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assert(MSD.SectionIndex && "Invalid section index!");
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LocalSymbolData.push_back(MSD);
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// External and undefined symbols are required to be in lexicographic order.
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std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
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std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
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// Set the symbol indices.
718
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
719
LocalSymbolData[i].SymbolData->setIndex(Index++);
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for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
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ExternalSymbolData[i].SymbolData->setIndex(Index++);
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for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
723
UndefinedSymbolData[i].SymbolData->setIndex(Index++);
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// The string table is padded to a multiple of 4.
726
while (StringTable.size() % 4)
727
StringTable += '\x00';
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void WriteObject(MCAssembler &Asm) {
731
unsigned NumSections = Asm.size();
733
// Compute the symbol -> symbol data map.
735
// FIXME: This should not be here.
736
DenseMap<const MCSymbol*, MCSymbolData *> SymbolMap;
737
for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
738
ie = Asm.symbol_end(); it != ie; ++it)
739
SymbolMap[&it->getSymbol()] = it;
741
// Create symbol data for any indirect symbols.
742
BindIndirectSymbols(Asm, SymbolMap);
744
// Compute symbol table information.
745
SmallString<256> StringTable;
746
std::vector<MachSymbolData> LocalSymbolData;
747
std::vector<MachSymbolData> ExternalSymbolData;
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std::vector<MachSymbolData> UndefinedSymbolData;
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unsigned NumSymbols = Asm.symbol_size();
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// No symbol table command is written if there are no symbols.
753
ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
754
UndefinedSymbolData);
756
// The section data starts after the header, the segment load command (and
757
// section headers) and the symbol table.
758
unsigned NumLoadCommands = 1;
759
uint64_t LoadCommandsSize =
760
SegmentLoadCommand32Size + NumSections * Section32Size;
762
// Add the symbol table load command sizes, if used.
764
NumLoadCommands += 2;
765
LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize;
768
// Compute the total size of the section data, as well as its file size and
770
uint64_t SectionDataStart = Header32Size + LoadCommandsSize;
771
uint64_t SectionDataSize = 0;
772
uint64_t SectionDataFileSize = 0;
774
for (MCAssembler::iterator it = Asm.begin(),
775
ie = Asm.end(); it != ie; ++it) {
776
MCSectionData &SD = *it;
778
VMSize = std::max(VMSize, SD.getAddress() + SD.getSize());
780
if (isVirtualSection(SD.getSection()))
783
SectionDataSize = std::max(SectionDataSize,
784
SD.getAddress() + SD.getSize());
785
SectionDataFileSize = std::max(SectionDataFileSize,
786
SD.getAddress() + SD.getFileSize());
789
// The section data is padded to 4 bytes.
791
// FIXME: Is this machine dependent?
792
unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
793
SectionDataFileSize += SectionDataPadding;
795
// Write the prolog, starting with the header and load command...
796
WriteHeader32(NumLoadCommands, LoadCommandsSize,
797
Asm.getSubsectionsViaSymbols());
798
WriteSegmentLoadCommand32(NumSections, VMSize,
799
SectionDataStart, SectionDataSize);
801
// ... and then the section headers.
803
// We also compute the section relocations while we do this. Note that
804
// computing relocation info will also update the fixup to have the correct
805
// value; this will overwrite the appropriate data in the fragment when it
807
std::vector<MachRelocationEntry> RelocInfos;
808
uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
809
for (MCAssembler::iterator it = Asm.begin(),
810
ie = Asm.end(); it != ie; ++it) {
811
MCSectionData &SD = *it;
813
// The assembler writes relocations in the reverse order they were seen.
815
// FIXME: It is probably more complicated than this.
816
unsigned NumRelocsStart = RelocInfos.size();
817
for (MCSectionData::reverse_iterator it2 = SD.rbegin(),
818
ie2 = SD.rend(); it2 != ie2; ++it2)
819
if (MCDataFragment *DF = dyn_cast<MCDataFragment>(&*it2))
820
for (unsigned i = 0, e = DF->fixup_size(); i != e; ++i)
821
ComputeRelocationInfo(Asm, *DF, DF->getFixups()[e - i - 1],
822
SymbolMap, RelocInfos);
824
unsigned NumRelocs = RelocInfos.size() - NumRelocsStart;
825
uint64_t SectionStart = SectionDataStart + SD.getAddress();
826
WriteSection32(SD, SectionStart, RelocTableEnd, NumRelocs);
827
RelocTableEnd += NumRelocs * RelocationInfoSize;
830
// Write the symbol table load command, if used.
832
unsigned FirstLocalSymbol = 0;
833
unsigned NumLocalSymbols = LocalSymbolData.size();
834
unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
835
unsigned NumExternalSymbols = ExternalSymbolData.size();
836
unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
837
unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
838
unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
839
unsigned NumSymTabSymbols =
840
NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
841
uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
842
uint64_t IndirectSymbolOffset = 0;
844
// If used, the indirect symbols are written after the section data.
845
if (NumIndirectSymbols)
846
IndirectSymbolOffset = RelocTableEnd;
848
// The symbol table is written after the indirect symbol data.
849
uint64_t SymbolTableOffset = RelocTableEnd + IndirectSymbolSize;
851
// The string table is written after symbol table.
852
uint64_t StringTableOffset =
853
SymbolTableOffset + NumSymTabSymbols * Nlist32Size;
854
WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
855
StringTableOffset, StringTable.size());
857
WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
858
FirstExternalSymbol, NumExternalSymbols,
859
FirstUndefinedSymbol, NumUndefinedSymbols,
860
IndirectSymbolOffset, NumIndirectSymbols);
863
// Write the actual section data.
864
for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
865
WriteFileData(OS, *it, *this);
867
// Write the extra padding.
868
WriteZeros(SectionDataPadding);
870
// Write the relocation entries.
871
for (unsigned i = 0, e = RelocInfos.size(); i != e; ++i) {
872
Write32(RelocInfos[i].Word0);
873
Write32(RelocInfos[i].Word1);
876
// Write the symbol table data, if used.
878
// Write the indirect symbol entries.
879
for (MCAssembler::indirect_symbol_iterator
880
it = Asm.indirect_symbol_begin(),
881
ie = Asm.indirect_symbol_end(); it != ie; ++it) {
882
// Indirect symbols in the non lazy symbol pointer section have some
884
const MCSectionMachO &Section =
885
static_cast<const MCSectionMachO&>(it->SectionData->getSection());
887
Section.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
888
if (Type == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) {
889
// If this symbol is defined and internal, mark it as such.
890
if (it->Symbol->isDefined() &&
891
!SymbolMap.lookup(it->Symbol)->isExternal()) {
892
uint32_t Flags = ISF_Local;
893
if (it->Symbol->isAbsolute())
894
Flags |= ISF_Absolute;
900
Write32(SymbolMap[it->Symbol]->getIndex());
903
// FIXME: Check that offsets match computed ones.
905
// Write the symbol table entries.
906
for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
907
WriteNlist32(LocalSymbolData[i]);
908
for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
909
WriteNlist32(ExternalSymbolData[i]);
910
for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
911
WriteNlist32(UndefinedSymbolData[i]);
913
// Write the string table.
914
OS << StringTable.str();
918
void ApplyFixup(const MCAsmFixup &Fixup, MCDataFragment &DF) {
919
unsigned Size = 1 << getFixupKindLog2Size(Fixup.Kind);
921
// FIXME: Endianness assumption.
922
assert(Fixup.Offset + Size <= DF.getContents().size() &&
923
"Invalid fixup offset!");
924
for (unsigned i = 0; i != Size; ++i)
925
DF.getContents()[Fixup.Offset + i] = uint8_t(Fixup.FixedValue >> (i * 8));
931
MCFragment::MCFragment() : Kind(FragmentType(~0)) {
934
MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
937
FileSize(~UINT64_C(0))
940
Parent->getFragmentList().push_back(this);
943
MCFragment::~MCFragment() {
946
uint64_t MCFragment::getAddress() const {
947
assert(getParent() && "Missing Section!");
948
return getParent()->getAddress() + Offset;
953
MCSectionData::MCSectionData() : Section(0) {}
955
MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
956
: Section(&_Section),
958
Address(~UINT64_C(0)),
960
FileSize(~UINT64_C(0)),
961
HasInstructions(false)
964
A->getSectionList().push_back(this);
969
MCSymbolData::MCSymbolData() : Symbol(0) {}
971
MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
972
uint64_t _Offset, MCAssembler *A)
973
: Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
974
IsExternal(false), IsPrivateExtern(false),
975
CommonSize(0), CommonAlign(0), Flags(0), Index(0)
978
A->getSymbolList().push_back(this);
983
MCAssembler::MCAssembler(MCContext &_Context, raw_ostream &_OS)
984
: Context(_Context), OS(_OS), SubsectionsViaSymbols(false)
988
MCAssembler::~MCAssembler() {
991
void MCAssembler::LayoutSection(MCSectionData &SD) {
992
uint64_t Address = SD.getAddress();
994
for (MCSectionData::iterator it = SD.begin(), ie = SD.end(); it != ie; ++it) {
997
F.setOffset(Address - SD.getAddress());
999
// Evaluate fragment size.
1000
switch (F.getKind()) {
1001
case MCFragment::FT_Align: {
1002
MCAlignFragment &AF = cast<MCAlignFragment>(F);
1004
uint64_t Size = OffsetToAlignment(Address, AF.getAlignment());
1005
if (Size > AF.getMaxBytesToEmit())
1008
AF.setFileSize(Size);
1012
case MCFragment::FT_Data:
1013
case MCFragment::FT_Fill:
1014
F.setFileSize(F.getMaxFileSize());
1017
case MCFragment::FT_Org: {
1018
MCOrgFragment &OF = cast<MCOrgFragment>(F);
1021
if (!OF.getOffset().EvaluateAsRelocatable(Target))
1022
llvm_report_error("expected relocatable expression");
1024
if (!Target.isAbsolute())
1025
llvm_unreachable("FIXME: Not yet implemented!");
1026
uint64_t OrgOffset = Target.getConstant();
1027
uint64_t Offset = Address - SD.getAddress();
1029
// FIXME: We need a way to communicate this error.
1030
if (OrgOffset < Offset)
1031
llvm_report_error("invalid .org offset '" + Twine(OrgOffset) +
1032
"' (at offset '" + Twine(Offset) + "'");
1034
F.setFileSize(OrgOffset - Offset);
1038
case MCFragment::FT_ZeroFill: {
1039
MCZeroFillFragment &ZFF = cast<MCZeroFillFragment>(F);
1041
// Align the fragment offset; it is safe to adjust the offset freely since
1042
// this is only in virtual sections.
1043
uint64_t Aligned = RoundUpToAlignment(Address, ZFF.getAlignment());
1044
F.setOffset(Aligned - SD.getAddress());
1046
// FIXME: This is misnamed.
1047
F.setFileSize(ZFF.getSize());
1052
Address += F.getFileSize();
1055
// Set the section sizes.
1056
SD.setSize(Address - SD.getAddress());
1057
if (isVirtualSection(SD.getSection()))
1060
SD.setFileSize(Address - SD.getAddress());
1063
/// WriteNopData - Write optimal nops to the output file for the \arg Count
1064
/// bytes. This returns the number of bytes written. It may return 0 if
1065
/// the \arg Count is more than the maximum optimal nops.
1067
/// FIXME this is X86 32-bit specific and should move to a better place.
1068
static uint64_t WriteNopData(uint64_t Count, MachObjectWriter &MOW) {
1069
static const uint8_t Nops[16][16] = {
1077
{0x0f, 0x1f, 0x40, 0x00},
1078
// nopl 0(%[re]ax,%[re]ax,1)
1079
{0x0f, 0x1f, 0x44, 0x00, 0x00},
1080
// nopw 0(%[re]ax,%[re]ax,1)
1081
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
1083
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
1084
// nopl 0L(%[re]ax,%[re]ax,1)
1085
{0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
1086
// nopw 0L(%[re]ax,%[re]ax,1)
1087
{0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
1088
// nopw %cs:0L(%[re]ax,%[re]ax,1)
1089
{0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
1090
// nopl 0(%[re]ax,%[re]ax,1)
1091
// nopw 0(%[re]ax,%[re]ax,1)
1092
{0x0f, 0x1f, 0x44, 0x00, 0x00,
1093
0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
1094
// nopw 0(%[re]ax,%[re]ax,1)
1095
// nopw 0(%[re]ax,%[re]ax,1)
1096
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00,
1097
0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
1098
// nopw 0(%[re]ax,%[re]ax,1)
1099
// nopl 0L(%[re]ax) */
1100
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00,
1101
0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
1104
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00,
1105
0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
1107
// nopl 0L(%[re]ax,%[re]ax,1)
1108
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00,
1109
0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}
1115
for (uint64_t i = 0; i < Count; i++)
1116
MOW.Write8 (uint8_t(Nops[Count - 1][i]));
1121
/// WriteFileData - Write the \arg F data to the output file.
1122
static void WriteFileData(raw_ostream &OS, const MCFragment &F,
1123
MachObjectWriter &MOW) {
1124
uint64_t Start = OS.tell();
1129
// FIXME: Embed in fragments instead?
1130
switch (F.getKind()) {
1131
case MCFragment::FT_Align: {
1132
MCAlignFragment &AF = cast<MCAlignFragment>(F);
1133
uint64_t Count = AF.getFileSize() / AF.getValueSize();
1135
// FIXME: This error shouldn't actually occur (the front end should emit
1136
// multiple .align directives to enforce the semantics it wants), but is
1137
// severe enough that we want to report it. How to handle this?
1138
if (Count * AF.getValueSize() != AF.getFileSize())
1139
llvm_report_error("undefined .align directive, value size '" +
1140
Twine(AF.getValueSize()) +
1141
"' is not a divisor of padding size '" +
1142
Twine(AF.getFileSize()) + "'");
1144
// See if we are aligning with nops, and if so do that first to try to fill
1145
// the Count bytes. Then if that did not fill any bytes or there are any
1146
// bytes left to fill use the the Value and ValueSize to fill the rest.
1147
if (AF.getEmitNops()) {
1148
uint64_t NopByteCount = WriteNopData(Count, MOW);
1149
Count -= NopByteCount;
1152
for (uint64_t i = 0; i != Count; ++i) {
1153
switch (AF.getValueSize()) {
1155
assert(0 && "Invalid size!");
1156
case 1: MOW.Write8 (uint8_t (AF.getValue())); break;
1157
case 2: MOW.Write16(uint16_t(AF.getValue())); break;
1158
case 4: MOW.Write32(uint32_t(AF.getValue())); break;
1159
case 8: MOW.Write64(uint64_t(AF.getValue())); break;
1165
case MCFragment::FT_Data: {
1166
MCDataFragment &DF = cast<MCDataFragment>(F);
1168
// Apply the fixups.
1170
// FIXME: Move elsewhere.
1171
for (MCDataFragment::const_fixup_iterator it = DF.fixup_begin(),
1172
ie = DF.fixup_end(); it != ie; ++it)
1173
MOW.ApplyFixup(*it, DF);
1175
OS << cast<MCDataFragment>(F).getContents().str();
1179
case MCFragment::FT_Fill: {
1180
MCFillFragment &FF = cast<MCFillFragment>(F);
1181
for (uint64_t i = 0, e = FF.getCount(); i != e; ++i) {
1182
switch (FF.getValueSize()) {
1184
assert(0 && "Invalid size!");
1185
case 1: MOW.Write8 (uint8_t (FF.getValue())); break;
1186
case 2: MOW.Write16(uint16_t(FF.getValue())); break;
1187
case 4: MOW.Write32(uint32_t(FF.getValue())); break;
1188
case 8: MOW.Write64(uint64_t(FF.getValue())); break;
1194
case MCFragment::FT_Org: {
1195
MCOrgFragment &OF = cast<MCOrgFragment>(F);
1197
for (uint64_t i = 0, e = OF.getFileSize(); i != e; ++i)
1198
MOW.Write8(uint8_t(OF.getValue()));
1203
case MCFragment::FT_ZeroFill: {
1204
assert(0 && "Invalid zero fill fragment in concrete section!");
1209
assert(OS.tell() - Start == F.getFileSize());
1212
/// WriteFileData - Write the \arg SD data to the output file.
1213
static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
1214
MachObjectWriter &MOW) {
1215
// Ignore virtual sections.
1216
if (isVirtualSection(SD.getSection())) {
1217
assert(SD.getFileSize() == 0);
1221
uint64_t Start = OS.tell();
1224
for (MCSectionData::const_iterator it = SD.begin(),
1225
ie = SD.end(); it != ie; ++it)
1226
WriteFileData(OS, *it, MOW);
1228
// Add section padding.
1229
assert(SD.getFileSize() >= SD.getSize() && "Invalid section sizes!");
1230
MOW.WriteZeros(SD.getFileSize() - SD.getSize());
1232
assert(OS.tell() - Start == SD.getFileSize());
1235
void MCAssembler::Finish() {
1236
DEBUG_WITH_TYPE("mc-dump", {
1237
llvm::errs() << "assembler backend - pre-layout\n--\n";
1240
// Layout the concrete sections and fragments.
1241
uint64_t Address = 0;
1242
MCSectionData *Prev = 0;
1243
for (iterator it = begin(), ie = end(); it != ie; ++it) {
1244
MCSectionData &SD = *it;
1246
// Skip virtual sections.
1247
if (isVirtualSection(SD.getSection()))
1250
// Align this section if necessary by adding padding bytes to the previous
1252
if (uint64_t Pad = OffsetToAlignment(Address, it->getAlignment())) {
1253
assert(Prev && "Missing prev section!");
1254
Prev->setFileSize(Prev->getFileSize() + Pad);
1258
// Layout the section fragments and its size.
1259
SD.setAddress(Address);
1261
Address += SD.getFileSize();
1266
// Layout the virtual sections.
1267
for (iterator it = begin(), ie = end(); it != ie; ++it) {
1268
MCSectionData &SD = *it;
1270
if (!isVirtualSection(SD.getSection()))
1273
SD.setAddress(Address);
1275
Address += SD.getSize();
1278
DEBUG_WITH_TYPE("mc-dump", {
1279
llvm::errs() << "assembler backend - post-layout\n--\n";
1282
// Write the object file.
1283
MachObjectWriter MOW(OS);
1284
MOW.WriteObject(*this);
1290
// Debugging methods
1294
raw_ostream &operator<<(raw_ostream &OS, const MCAsmFixup &AF) {
1295
OS << "<MCAsmFixup" << " Offset:" << AF.Offset << " Value:" << *AF.Value
1296
<< " Kind:" << AF.Kind << ">";
1302
void MCFragment::dump() {
1303
raw_ostream &OS = llvm::errs();
1305
OS << "<MCFragment " << (void*) this << " Offset:" << Offset
1306
<< " FileSize:" << FileSize;
1311
void MCAlignFragment::dump() {
1312
raw_ostream &OS = llvm::errs();
1314
OS << "<MCAlignFragment ";
1315
this->MCFragment::dump();
1317
OS << " Alignment:" << getAlignment()
1318
<< " Value:" << getValue() << " ValueSize:" << getValueSize()
1319
<< " MaxBytesToEmit:" << getMaxBytesToEmit() << ">";
1322
void MCDataFragment::dump() {
1323
raw_ostream &OS = llvm::errs();
1325
OS << "<MCDataFragment ";
1326
this->MCFragment::dump();
1328
OS << " Contents:[";
1329
for (unsigned i = 0, e = getContents().size(); i != e; ++i) {
1331
OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
1333
OS << "] (" << getContents().size() << " bytes)";
1335
if (!getFixups().empty()) {
1338
for (fixup_iterator it = fixup_begin(), ie = fixup_end(); it != ie; ++it) {
1339
if (it != fixup_begin()) OS << ",\n ";
1348
void MCFillFragment::dump() {
1349
raw_ostream &OS = llvm::errs();
1351
OS << "<MCFillFragment ";
1352
this->MCFragment::dump();
1354
OS << " Value:" << getValue() << " ValueSize:" << getValueSize()
1355
<< " Count:" << getCount() << ">";
1358
void MCOrgFragment::dump() {
1359
raw_ostream &OS = llvm::errs();
1361
OS << "<MCOrgFragment ";
1362
this->MCFragment::dump();
1364
OS << " Offset:" << getOffset() << " Value:" << getValue() << ">";
1367
void MCZeroFillFragment::dump() {
1368
raw_ostream &OS = llvm::errs();
1370
OS << "<MCZeroFillFragment ";
1371
this->MCFragment::dump();
1373
OS << " Size:" << getSize() << " Alignment:" << getAlignment() << ">";
1376
void MCSectionData::dump() {
1377
raw_ostream &OS = llvm::errs();
1379
OS << "<MCSectionData";
1380
OS << " Alignment:" << getAlignment() << " Address:" << Address
1381
<< " Size:" << Size << " FileSize:" << FileSize
1383
for (iterator it = begin(), ie = end(); it != ie; ++it) {
1384
if (it != begin()) OS << ",\n ";
1390
void MCSymbolData::dump() {
1391
raw_ostream &OS = llvm::errs();
1393
OS << "<MCSymbolData Symbol:" << getSymbol()
1394
<< " Fragment:" << getFragment() << " Offset:" << getOffset()
1395
<< " Flags:" << getFlags() << " Index:" << getIndex();
1397
OS << " (common, size:" << getCommonSize()
1398
<< " align: " << getCommonAlignment() << ")";
1400
OS << " (external)";
1401
if (isPrivateExtern())
1402
OS << " (private extern)";
1406
void MCAssembler::dump() {
1407
raw_ostream &OS = llvm::errs();
1409
OS << "<MCAssembler\n";
1410
OS << " Sections:[";
1411
for (iterator it = begin(), ie = end(); it != ie; ++it) {
1412
if (it != begin()) OS << ",\n ";
1418
for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
1419
if (it != symbol_begin()) OS << ",\n ";